Bioavailability indices for uranium: Effect of concentration in eleven soils

Abstract

Bioavailability indices have not been developed for uranium (U) in soils. Eleven soils, covering a broad range in soil properties, were treated to achieve U concentrations ranging from background to 10,000 mg U/kg dry soil. Uptake by radish and beans, accumulation by earthworms and extraction with two chemicals were investigated. The extraction efficiency of NaHCO3 was very high and reflected total soil U levels rather than bioavailable soil U levels. The extraction efficiency of CH3COONH4 was lower and was well correlated to the concentration ratios for plants and earthworms. These latter three indices were all negatively correlated to soil cation exchange capacity and organic matter contents. These indices were not constant across soil U concentrations. In several soils, the bioavailability of U was at a minima in the range of 10 to 100 mg U/kg dry soil. The mechanism for this is not clear, but sublethal toxicity may be involved. © 1992 Springer-Verlag New York Inc.